1. Field of the Invention
The present invention relates to an image forming apparatus employing electrophotographic printing or electrostatic printing and a control method therefor and, more particularly, to image adjustment control of a color image forming apparatus.
2. Description of the Related Art
Conventional color image forming apparatuses, especially tandem type (e.g., 4D type) image forming apparatuses cannot prevent gradual changes in output image density and density balance as the number of output sheets increases or the environment changes.
To prevent the foregoing problems, a variety of adjustment processes have been proposed. For example, various proposals are made in association with automatic maintenance processing or adjustment processing executed automatically during the image forming operation (e.g., Japanese Patent Laid-Open No. 10-243235). For example, there is proposed an image forming apparatus having a means for determining the necessity to adjust image forming conditions during the image forming operation, and a means for adjusting the image forming conditions. In this image forming apparatus, when it is determined that adjustment is necessary, adjustment of the image forming conditions is suspended until the end of image formation in process.
According to this technique, when it is determined that image adjustment processing is necessary, adjustment is suspended until the end of an image forming job in process. After the job ends, image adjustment processing must be done. Image adjustment processing always requires a down time after the end of a job. When jobs are successively performed, the user must wait a long time for a printout.